Process of dehydrating nitrocellulose and reducing the fire risk thereof



50 prevailing during the percolation: and shouldalso be: capable of taking up or ab fibers and PAUL C. SEEL, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COMPANY, .OF ROCHESTER, NEW YORK, A GGRPORATION OF NEW YORK.

THEREOF.

rnoonss or DEH'YDRA'IING NITROCELLULOSE AND REDUCING THE rmn nrsn No Drawing.

To all to hem it-may 0mm Be it known that I, PAUfJC. SEEL, a citi-' zen of the United States of America, residing at Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Processes of Dehydrating Nitrocellulose and Reducing the Fire Risk Thereof, of'which the following is a full, clear, and exact specification.

This invention relates to a rocess of handling nitrocellulose between the washing operations and the plasticizing operations. The chief object of the invention is to provide a novel stepor steps by which all harmful amounts of water may be removed from the washed nitrocellulose fibers without increasing the fire risk, such fibers being kept in a condition of comparativesafety up to the time when they are incorporated into suitable compositions or forms. Other objects will hereinafter appear.

After cellulose fibers are nitrated, the acid is removed therefrom by washing in water or aqueous solutions. But the-amount of water clinging to the washed fibers cannot be reduced by wringing or like mechanical means to a point where the nitrocellulose is ready for incorporation into the usual plastic compositions. While the retained moisture may be finally removed by evaporation, such a step has proven in practice to be a very dangerous one, because the hazard of fire, or even of explosion, is very greatly increased when the nitrocellulose is dry. For safety during the entire period of storage and transport, the nitrocellulose should be kept in a wetted condition, the term wetted applying herein to fibers intermingled with non-aqueous liquids-as well as when intermingled with water.

In order to remove the water and at th same time keep the nitrocellulose fibers safely wetted a suitable liquid should be allowed to ercolate through the mass of absorb the remnant of moisture which remains intermingled therewithafter the washing and wringing operations. The liquid thus used should be ahonsolvent of the nitrated cotton, under the conditions sorbing. the water within itself without specification of Letters Patent. Patented N 29, 1921 slim-mee alea aa ust 9, 1920. Serial no. 402,478.

excess of liquid is removed, leaving enough liquid intermingled with the fibers of nitrocellulose to keep the latter suitably wetted for fire prevention.

I have found that effectively anhydrous normal butyl alcohol and effectively anhydrous isobutyl alcohol and a mixture of them have each the necessary properties for successful use in the above described opera tions. Moreover, because of the low volatility of these liquids, the amount of them which is left on the fibers will keep the latter sufiiciently wetted to minimize the fire hazard over a considerable period of time during storage and transportation prior to the final use of the fibers. These alcohols even in the ordinary commercial grades have the property, when suitably dehydrated, of talc ing up a considerable amount of water with out harm to themselves or subsequent products. By effectively anhydrous I, therefore, mean that suflicient water has been removed from these alcohols by usual dehydrating methods prior to percolation to enable them to absorb a useful amount of water when intermingled with moist nitrocellulose fibers. Of course, the commercial grades of these alcohols may contain small amounts of other substances without impairing their effectiveness. Both of these alcohols boil above 100 degrees C. and I generically designate them as butylic alcohols of low volatility.

I will now describe, by way of illustration, the preferred embodiment of my invention. The fibers of nitrocellulose, moist with the final wash water, are mechanically treated, as in a centrifuge, to press or wring out as much water as possible, the water remaining being, for example, from forty to sixty er cent. by weight of the nitrocellulose. ormal butyl alcohol of the commercial grade (comprising in typical samples over eighty per cent. of this alcohol and boiling approximately at 115 to 117 degrees C.) is

then thoroughly percolated through the fivet'o ten times the. weight ofni'trooellulos'eto be treated. Afterthe water has been ab? sorbed, by the percolated liquid, the excess of alcohol is removed-mechanically, say in a centrifugej 'I hisfremovaI'may Becarried to the oint where the amount of normal butyl alcoliol remaining on the nitrocellulose fibers becomes, for instance, forty to sixty per cent. by weight of the latter. Of course any other safe per cent. couldbe retained. The nitrocellulose, thus wetted by this retained alcohol, can be kept in storage or transported with low fire risk for a considerable length of time, the normal butyl alcohol being of a usefully low volatility, and consequently remaining in place on the fibers. Isobutyl alcohol either alone or in admixture with normal butyl alcohol can also be used in the same way.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is: Y

1. In the process of preparing nitrocellu lose, the step which comprises treating nitrocellulose carrying water, with a li uid comprised chiefly of effectively anhy rous butylic alcohol of low volatility. 2. In'the process of preparing nitrocellulose, the step which comprises treating nitrocellulose carrying water with efl'ectively anhydrous normal butyl alcohol.

maining with the fibers, and removing the excess of said alcohol .from the fibers, the remaining alcohol intermingled with the fibers, reducing the fire risk.

5. In the process of preparing nitrocellulose, the step which comprises treating one part of nitrocellulose fibers carrying forty to sixty per cent. of water with from five to ten parts of commercial anhydrous normal butyl alcohol.

Signed at Rochester, New York, this 2nd day of August, 1920.

PAUL C. SEEL. 

